The identification marking of products is becoming increasingly important in almost every branch of industry. For example, it is often necessary to apply marks such as production dates, expiration dates, bar codes, company logos, serial numbers, images, and the like. Most of these markings are currently executed using conventional techniques, such as printing or labeling. However, contactless and rapid marking with lasers is gaining growing importance, especially for plastics. The use of lasers permits the high-speed application of graphics, bar codes, and the like without any additional pre-treatment of the plastic to improve adhesion. In addition, laser marked images are durable and abrasion-resistant, since they are within the body of the plastic film.
Previously, many plastics have proven to be very difficult or even impossible to mark through the use of lasers. These include many common polyolefins, such as polyethylene, polypropylene, ethylene vinyl acetate, polybutene, and polyisoprene. Particularly, laser irradiation of polyolefins, even at very high power, produces a weak, virtually illegible mark since the absorption coefficient is not sufficiently high to induce a color change.
In addition, when lasers are used to mark a polyolefin film, the pigment can overheat in the direct vicinity of the irradiation site and distort or decompose the plastic. As a result, the plastic layer scatters the light and reduces the contrast of the mark. Specifically, the definition of the image becomes distorted or irregular, thereby rendering the mark commercially less effective or completely useless.
Thus, the industry is in need of a marking solution that allows for a smaller unit of production with customized information that can be included on individual packages. Graphics changes with traditional printing methods have proven to be expensive and require longer lead times due to the printing plates and the generation of negatives. It is often difficult to achieve smaller order lots with traditional printing methods, such as flexography or rotogravure. The use of laser marking therefore potentially allows for economical methods of converting and allows the end user to reduce waste from aged or obsolete inventory and/or frequent change orders. The medical applications field and regulation are also beginning to require specific unit track and trace, which would follow the on-demand marking solution noted in the presently disclosed subject matter.
The disclosed film provides a laser-imageable film comprising at least one polyolefin that provides high-contrast and good laser marking while simultaneously retaining the smooth, non-distorted surface of the polymer film.